The invention relates to a sensor device and a method of producing a sensor device with a sensor, which is embodied, in particular, as a pressure sensor.
European patent EP 0 548 470 B1 discloses a sensor device with a micromechanical pressure sensor. The pressure sensor is protected by a corrosion-resistant covering made up of a plurality of layers. A silicone gel serves as the first layer of the covering and as a pressure medium. The micromechanical pressure sensor is fitted in a housing.
It has been known, in the context of micromechanical semiconductor sensors, to form the sensor element and a signal processing unit integrally in the semiconductor sensor. In the signal processing unit, the measuring signal of the sensor element is converted by means of a characteristic curve and, if appropriate, by correction with correction values, into an output signal. The output signal is then fed to, say, an engine control system. If the sensor device is arranged in a manifold of an intake tract of an internal combustion engine, the sensor device senses the intake-pipe pressure. That information is needed by the engine control system for calculating the amount of fuel injected.
On account of the fabrication variations in the production of the sensors, the reference between the respective measured variable, for example a pressure, and the respective measuring signal of the sensor varies from sensor to sensor. Therefore, the sensors must be calibrated in order to establish a unique assignment between the measured variable and the respective output signal of the sensor.
It is known in the art to encapsulate the sensors with a casting compound. This protects them against the working media which, in some cases, are chemically aggressive. An exact calibration of the sensor is only possible after the encapsulation of the sensor with the casting compound, since the reference between the measured variable and the measuring signal of the sensor may be altered by the casting compound. If, however, the sensor is integrally formed by the sensor element and the signal processing unit, the signal processing unit can no longer be electrically contacted in order to carry out a calibration after the encapsulation of the sensor.
The object of the invention is to provide a sensor device and a method of producing the sensor device which overcomes the above-noted deficiencies and disadvantages of the prior art devices and methods of this kind, and which allows the sensor device to be exactly calibrated.
With the above and other objects in view there is provided, in accordance with the invention, a method of producing a sensor device, which comprises:
providing a housing part formed with a chamber and a groove;
placing a sensor having a sensor element and a signal processing unit in the chamber;
electrically connecting at least one contact element to the signal processing unit, the contact element having a contact region formed in the groove;
encapsulating the sensor element with a casting compound and subsequently electrically contacting the contact region in the groove of the housing part;
calibrating the sensor by aligning a characteristic curve of the sensor element with a predetermined characteristic curve and transmitting calibration data via the at least one contact element to the signal processing unit and storing the calibration data in the signal processing unit;
introducing sealing compound into the groove and sealing the contact region; and
bringing a cover into contact with the sealing compound in the groove, and sealing the groove, the sealing compound and the cover together such that the chamber communicates only with a working medium.
In other words, the invention is distinguished in that the contact region of the contact elements can be electrically contacted well for calibrating and can be insulated well after calibration by introducing the sealing compound. Consequently, effective protection against influencing of the signal processing by interference signals and protection against corrosion are ensured. The invention makes simple and low-cost production of the sensor device possible.
In accordance with an added feature of the invention, the calibration data include at least one correction value.
In accordance with an additional feature of the invention, the calibration data comprise a calibrated characteristic curve of the sensor element.
With the above and other objects in view there is also provided, in accordance with the invention, a sensor device, comprising:
a housing part formed with a chamber and a groove;
a sensor having a sensor element and a signal processing unit;
fitted in the chamber and encapsulated with a casting compound;
a contact element for transmitting calibration data during a calibration of the sensor electrically connected to the signal processing unit, the contact element having a contact region formed in the groove of the housing part;
an amount of sealing compound introduced in the groove and sealing the contact region; and
a cover in contact with the sealing compound in the groove, whereby the groove, the sealing compound, and the cover interact in such a way that the chamber communicates only with a working medium.
In accordance with another feature of the invention, the sealing compound is an adhesive sealing compound and the cover is adhesively fixed in the groove.
In accordance with a concomitant feature of the invention, the housing part is formed with a further groove, supporting feet of an electrical component are fitted in the further groove, and the adhesive sealing compound has been introduced into the further groove.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a sensor device and method of producing a sensor device it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.